This invention relates to a cushioning system for an article of footwear. In particular, the cushioning system includes a fluid-filled bladder having separate reservoir chambers. The chambers are in fluid communication with each other, and a control device dynamically-distributes and regulates pressure within the chambers based on sensed and user input criteria.
Articles of footwear, such as the modern athletic shoes, are highly refined combinations of many elements which have specific functions, all of which work together for the support and protection of the foot. Athletic shoes today are as varied in design and purpose as are the rules for the sports in which the shoes are worn. Tennis shoes, racquetball shoes, basketball shoes, running shoes, baseball shoes, football shoes, walking shoes, etc. are all designed to be used in very specific, and very different, ways. They are also designed to provide a unique and specific combination of traction, support and protection to enhance performance.
Moreover, physical differences between wearers of a specific shoe, such as differences in each user""s weight, foot size, shape, activity level, and walking and running style, make it difficult to economically optimize a mass produced shoe""s performance to a particular individual.
Closed-celled foam is often used as a cushioning material in shoe soles and ethylene-vinyl acetate copolymer (EVA) foam is a common material. In many athletic shoes, the entire midsole is comprised of EVA. While EVA foam can be cut into desired shapes and contours, its cushioning characteristics are limited. One of the advantages of fluid, in particular gas, filled bladders is that gas as a cushioning component is generally more energy efficient than closed-celled foam. Cushioning generally is improved when the cushioning component, for a given impact force, spreads the impact force over a longer period of time, resulting in a smaller impact force being transmitted to the wearer""s body. Thus, fluid-filled bladders are routinely used as cushions in such shoes to increase shoe comfort, enhance foot support, decrease wearer fatigue, and reduce the risk of injury and other deleterious effects. In general, such bladders are comprised of elastomeric materials which are shaped to define at least one pressurized pocket or chamber, and usually include multiple chambers arranged in a pattern designed to achieve one or more of the above-stated characteristics. The chambers may be pressurized with a variety of different mediums, including air, various gases, water, or other liquids.
Numerous attempts have been made to improve the desirable characteristics associated with fluid-filled bladders by attempting to optimize the orientation, configuration and design of the chambers. In U.S. Pat. No. 2,080,469 to Gilbert, bladders have been constructed with a single chamber that extends over the entire area of the sole. Alternatively, bladders have included a number of chambers fluidly interconnected with one another. Examples of these types of bladders are disclosed in U.S. Pat. No. 4,183,156 to Rudy, and U.S. Pat. No. 900,867 to Miller. However, these types of bladder constructions have been known to flatten and xe2x80x9cbottom outxe2x80x9d when they receive high impact pressures, such as experienced in athletic activities. Such failures negate the intended benefits of providing the bladder.
In an effort to overcome this problem, bladders have been developed with the chambers fluidly connected to each other by restricted openings. Examples of these bladders are illustrated in U.S. Pat. No. 4,217,705 to Donzis, U.S. Pat. No. 4,129,951 to Petrosky, and U.S. Pat. No. 1,304,915 to Spinney. However, these bladders have tended to either be ineffective in overcoming the deficiencies of the non-restricted bladders, or they have been too expensive to manufacture.
Bladders are also disclosed in patents that include a number of separate chambers that are not fluidly connected to each other. Hence, the fluid contained in any one chamber is precluded from passing into another chamber. One example of this construction is disclosed in U.S. Pat. No. 2,677,906 to Reed. Although this design obviates xe2x80x9cbottoming outxe2x80x9d of the bladder, it also requires each chamber to be individually pressurized, thus, the cost of production can be high.
Another problem with these known bladder designs is that they do not offer a way for a user to individually adjust the pressure in the chambers to optimize their shoes"" performance for their particular sport or use. Several inventors have attempted to address this issue by adding devices that make the chamber pressure adjustable. For example, U.S. Pat. No. 4,722,131 to Huang discloses an open system type of air cushion. The air cushion has two cavities, with each cavity having a separate air valve. Thus, each cavity can be inflated to a different pressure by pumping in or releasing air as desired.
However, in such systems, a separate pump is required to increase the pressure in the cavities. Such a pump would have to be carried by the user if it is desired to inflate the cavities away from home, inconveniencing the user. Alternatively, the pump could be built into the shoe, adding weight to the shoe and increasing the cost and complexity. Additionally, open systems tend to lose pressure rapidly due to diffusion through the bladder membrane or leakage through the valve. Thus, the pressure must be adjusted often.
A significant improvement over this type of design is found in U.S. Pat. No. 5,406,719 to Potter (xe2x80x9cPotterxe2x80x9d), the disclosure of which is hereby incorporated by reference. Potter controllably links a plurality of chambers within a bladder with at least one variable-volume fluid reservoir such that the pressure in each chamber may be manually adjusted by a user modulating selected control links and the volume of the reservoir. The chambers may be oriented to allow chambers of different pressure in areas corresponding with different areas of the foot. For example, to correct over-pronation, pressure in chambers located on the medial side of the shoe can be selectively increased by the user.
The system in Potter is also closed to the atmosphere. Accordingly, pressure in the system may be higher than ambient pressure. Moreover, dirt and other debris cannot enter the system.
However, since Potter requires manual adjustment, the pressure in the various chambers cannot be dynamically modulated or adjusted during use of the shoe. Accordingly, considerable user effort is required to xe2x80x9cfine tunexe2x80x9d the performance of the shoe for a particular use and individual, and such adjustments must be re-done by the user when the sport or activity changes.
In recent years, consumer electronics have become increasingly more reliable, durable, light-weight, economical, and compact. As a result, the basic elements of a miniaturized fundamental control system, such as a central processing unit, input/output device, data sensing devices, power supplies, and micro actuators are now commercially available at reasonable prices. Such systems are small, light-weight, and durable enough to be attached to an article of footwear, such as a shoe, without compromising the shoe""s performance.
A control system to permit dynamic adjustment to the pressure in a single chamber cushioning bladder is disclosed in U.S. Pat. No. 5,813,142 to Demon (xe2x80x9cDemonxe2x80x9d), the disclosure of which is hereby incorporated by reference. In Demon, a plurality of single-chamber independent bladders are secured within a shoe and in fluid communication with ambient air through fluid ducts. A control system monitors the pressure in each bladder. Each duct includes a flow regulator, that can be actuated by the control system to any desired position such that the fluid duct can be modulated to any position between and including being fully open and fully closed. The control system monitors the pressure in each of the bladders, and opens the flow regulator as programmed based on detected pressure in each bladder.
Despite the benefits of using an on-board control system to dynamically modulate bladder pressure in each bladder of Demon, the specific implementation of this concept taught by Demon adversely affects performance of the bladder as a cushion, thereby significantly limiting the commercial viability of the concept. For example, the plurality of bladders in Demon each have their own reservoir, which is preferably ambient air. Accordingly, the static pressure in each bladder cannot exceed ambient pressure. In practice, it is desirable for the static pressure in the bladder to be higher than ambient pressure. Such higher pressures the bladder to return to its neutral position following impact, prevents bottoming out of the bladder, and improves the cushioning ability, or feel, of the bladder.
Also, like other bladder configurations that exhaust to ambient air, the bladders in Demon are prone to collect dirt and other debris through their exit/inlet port, particularly when a user wears the shoe outdoors, such as when running on wet pavement. Moreover, Demon neither teaches nor suggests dynamically-modulating pressure between at least two chambers within the same bladder thereby allowing the control system to optimize performance within all areas of the bladder without compromising the integrity of the system, and without requiring multiple bladders within the same shoe.
Accordingly, despite the known improvements to bladder designs, there remains a need for a cost effective, closed-system, multi-chamber bladder that allows pressure in each chamber to be dynamically distributed, adjusted, and regulated between each chamber based on real-time sensed and user input criteria to optimize the desirable characteristics of the bladder while the shoe is being worn by its user.
In addition to other benefits that will become apparent in the following disclosure, the present invention fulfills this need.
The present invention is a cushioning system for an article of footwear that includes a fluid-filled bladder having a plurality of separate sealed cushioning chambers. Separate reservoir chambers can also be placed in fluid communication with the cushioning chambers. The chambers are in fluid communication with each other, and a control device dynamically-distributes and regulates pressure within the chambers based on sensed and user input criteria by modulating the level of fluid communication between each of the chambers and, if installed, the reservoir chambers.
In a preferred embodiment, the control system includes a central processing unit (CPU), pressure sensing devices, and electronically-actuated, CPU-commanded valves that work in conjunction to control fluid communication between the chambers, and if desired, with a variable volume reservoir to optimize performance of the cushioning system for a particular wearer and activity.